On Dec. 15, Chapman will reveal on The Dr. Oz Show that he's battling severe hypertension and needs a kidney transplant. But he has to lose about 75 pounds first to become a viable candidate for organ transplant.
Chapman says he is ready for the fight of his life. "Whatever I can do for the longevity of my life, I'm going to do," he tells PEOPLE.
But he admits he's very nervous about getting a kidney transplant. "I'm afraid to get one because of all the unknown things. You can put a kidney in your body – and somewhere down the line your body might reject it. I'm not saying I don't want to go through with it but it's a little scary. It's a big decision," he says.
Support from FriendsFortunately, Chapman has Dr. Oz – and a close friend on his side. "The cool thing is Dr. Oz is passionate about this," says Chapman. "He brought a doctor into my life that is going to help me. When you have other people in your corner, it makes it a little bit easier."
Chapman's 30 Rock co-star Kevin Brown, who plays "Dot Com," will also be there for his pal. "He's a great support," says Chapman. "I can come to him with anything. He has a few pounds to lose so we're going to do this together."
Ignoring the SignsAnd there's another reason he's taking his story public – he wants to make sure people take their health seriously.
"At the end of the day if I can bring awareness to this problem, I'll do whatever I can do," says Chapman, who will admit on Dr. Oz’s show that he ignored his high blood pressure for years. "I was a celebrity bodyguard. I didn't keep the best hours or choose the best food when I was on the road."
He also didn't visit the doctor on a regular basis. "Even though you don't feel anything you need to get an annual check-up," he says. "It doesn't matter if you feel fine because I felt fine."